Preheat your grill or grill pan over medium-high heat.
Wash all the vegetables. Slice the zucchini into 1/4-inch thick rounds, cut the bell pepper into quarters and remove the seeds, and cut the red onion into thick slices. Leave the cherry tomatoes whole.
In a large bowl, combine the sliced zucchini, bell pepper, onion, and cherry tomatoes.
Drizzle the olive oil over the vegetables and sprinkle with salt, black pepper, garlic powder, and oregano. Toss well to ensure all vegetables are evenly coated.
Using tongs, place the vegetables directly onto the grill or grill pan.
Grill the vegetables for about 6-8 minutes on each side, or until they have nice grill marks and are tender. Keep an eye on the cherry tomatoes as they may cook faster and may pop when overcooked.
Remove the vegetables from the grill and let them cool slightly before serving.